Anderson's Salamander (Ambystoma andersoni)

Anderson’s salamander exhibits some highly unusual and distinct features, indicative of its evolutionary distinctiveness, including its rare “neotenous” life history, whereby the species never develops into an adult but instead retains its juvenile characteristics throughout life, essentially achieving reproductive maturity whilst still in its undeveloped larval form. This would be akin to a tadpole being able to breed without ever turning into a frog. The species is totally aquatic, spending its whole life in the same body of water (Lake Zacapu). This lake is currently suffering from pollution which poses a major threat to the survival of the species.

Evolutionary Distinctiveness
Order: Caudata
Family: Ambystomatidae
The family Ambystomatidae or “the mole salamanders” is included within the four earliest or most primitive family lineages of the order “Caudata” (the salamanders), diverging from all other salamanders in the Early Cretaceous period over 140 million years ago, around five million years before the koala and dolphin lineages diverged from their common ancestor. The small number of species that represent the genus Ambystoma are highly evolutionarily distinct members of both the salamanders and the amphibians as a whole.Anderson’s salamander exhibits some highly unusual and distinct features, indicative of its evolutionary distinctiveness, including its rare “neotenous” life history, whereby the species never develops into an adult but instead retains its juvenile characteristics throughout life, essentially achieving reproductive maturity whilst still in its undeveloped larval form. There are a couple of theories for why neoteny (also referred to as paedomorphosis) develops in some mole salamanders. One idea is that the production or effectiveness of the hormone thyroxine is compromised, either by the species living in water bodies containing insufficient iodine (which is required in the manufacture of thyroxine by the body) or in water temperatures that are too cold for the thyroxine to be effective. This impacts upon the development of the species and sexually mature adults never develop adult characteristics but remain in the larval form. A second theory suggests that species evolving in pools surrounded by hostile terrestrial environments develop aquatic lives to obviate the need to exit the relative safety of their watery home. This is a common trait in species that inhabit high-elevation ponds.

Description
Anderson’s salamander is an Ambystomatid or mole salamander found only in Lake Zacapu near Zacapu, Mexico at an elevation of 2,000 meters above sea level. Mole salamanders are medium to large, stocky salamanders, usually measuring between 90 to 350mm from the tip of the nose to the end of the tail, which salamanders retain throughout their life. Males are often larger than females, owing to their longer tails. Ambystomatids generally exhibit both aquatic “neotenic” larval (or aquatic and permanently juvenile in form with external, feathery gills) and terrestrial “metamorphosed” (or ground-dwelling, fully developed adult in form with reduced gills) stages in their wild populations. Ambystomatids are often boldly patterned as adults, with well-developed “costal” grooves (successive vertical grooves along the sides of the body), especially the metamorphosing varieties. They have a rather flattened body with a wide, flattened head, a large mouth and smooth skin with many glands. The tail is roundish or laterally compressed, and, during the breeding season, males have a very swollen cloacal zone (the region around the reproductory and excretory opening in amphibians located underneath the base of the tail).Like all neotenic Ambystoma species, Anderson’s salamander retains its larval features into adulthood. The mature salamander has medium-sized external gills with bright red filaments, and a prominent caudal (or tail) fin. It grows to a length of around 214 mm, with the tail accounting for about 40% of this measurement. A dorsal fin extends as a low ridge from the base of the gill rakers along the back to the base of the tail, where it rises about 13 mm to form the dorsal tail fin. This species has a large head and small, stocky limbs, as do the larvae. The toes are short and pointed with a slight degree of webbing. The skin colouration is a complex pattern of black blotches (some interconnected) on a red-brown base.

Ecology
Anderson’s salamanders are totally aquatic and spend their whole lives in the same body of water. The species is paedomorphic (or permanently juvenile in physical characteristics), and reaches sexual maturity whilst still having the appearance of a larval salamander. This would be akin to a tadpole being able to breed without ever turning into a frog. It requires a clean, cool aquatic habitat and is found only in Lake Zacapu and the spring-fed streams and canals associated with the lake. Once the eggs are laid in water they are left to develop with no further participation by either parent. This species does not exhibit parental care.Anderson’s salamanders do not metamorphosise from larval to adult form in nature, and individuals that have been artificially induced to metamorphosise with thyroid hormone in the laboratory do not thrive. The diet consists largely of snails and crawfish.

Habitat
Its habitat is that of Lake Zacapu, a small lake near Zacapu, sitting at an altitude of 2000 meters above sea level. The lake is located within the Mesa Central portion of Mexico, an area home to many neotenic Ambystoma species. Lake Zacapu (or Lago de Zacapu) is temperate, with low salinity, and the Anderson’s salamander inhabits the main body of the lake and the spring-fed streams and canals associated with it, requiring a clean, cool aquatic habitat in order to survive.
Distribution
Lake Zacapu (Lago Zacapu) and its surrounding streams near Zacapu, located in north-western Michoacan within the Mesa Central portion of Mexico at an altitude of 2000 metres above sea level.
Population Estimate
Unknown.
Population Trend
Anderson’s salamander is not currently rare in its small area of occupancy, but it is considered to be in decline by the IUCN Red List of Threatened Species.

Status
Listed as Critically Endangered in the IUCN Red List of Threatened Species because its extent of occurrence is less than 100km sq. and its area of occupancy is less than 10km sq., all individuals are in a single subpopulation, and there is continuing decline in the extent and quality of the lake habitat around the city of Zacapu.
Threats
The major threat to the wild population is the pollution of Lake Zacapu, its sole habitat location. Additionally, the animals are heavily fished for food and predatory fish have been introduced into the lake which may pose a severe problem if they prey extensively on the declining populations of Anderson’s salamander.
Conservation Underway
Anderson’s salamander does not occur in any protected area but the species could undergo a population recovery if Lake Zacapu can be kept clean and its ecosystem restored, including the control of introduced predatory fish and general levels of resource extraction from the lake and its associated streams and canals. Studies are needed to evaluate the sustainability of the harvest as well as on the impacts of introduced predatory fish. The species is protected under the category Pr (Special Protection) by the Government of Mexico.

Blunt-headed Salamander (Ambystoma amblycephalum)

The blunt-headed salamander is a metamorphosing species of mole salamander, which means that it can make the full transition from aquatic larval form to a terrestrial adult form in its lifetime. The adult spends the majority of its time on land in a mosaic of natural grasslands and pine-oak forests. It is highly evolutionarily distinct, the family diverging from all other salamanders in the Early Cretaceous period over 140 million years ago, around five million years before the koala and dolphin lineages diverged from their common ancestor. Today, the desiccation, pollution and conversion of former ponds, small reservoirs, and open habitat to row crops, represents the main threat to the species’ survival.

Evolutionary Distinctiveness
Order: Caudata
Family: Ambystomatidae
The family Ambystomatidae or “the mole salamanders” is included within the four earliest or most primitive family lineages of the order “Caudata” (the salamanders), diverging from all other salamanders in the Early Cretaceous period over 140 million years ago, around five million years before the koala and dolphin lineages diverged from their common ancestor. The small number of species that represent the genus Ambystoma are highly evolutionarily distinct members of both the salamanders and the amphibians as a whole.The blunt-headed salamander is capable of reaching sexual maturity in its neotenous form, retaining its aquatic larval characteristics such as fins and gills throughout its life. However, it is also able to metamorphose into the adult form and live a terrestrial life. Although this species has been little-studied, there are a couple of theories that may explain why some populations of the blunt-headed salamander do not metamorphose. One idea is that the production or effectiveness of the hormone thyroxine is compromised, either by the species living in water bodies containing insufficient iodine (which is required in the manufacture of thyroxine by the body) or in water temperatures that are too cold for the thyroxine to be effective. This impacts upon the development of the species and sexually mature adults never develop adult characteristics but remain in the larval form. A second theory suggests that species evolving in pools surrounded by hostile terrestrial environments develop aquatic lives to obviate the need to exit the relative safety of their watery home. This is a common trait in species that inhabit high-elevation ponds. Since the blunt-headed salamander inhabits various ponds across its range, and is able to disperse between them in its metamorphosed form, it is possible that the conditions in some of these ponds are not conducive to metamorphosis.
Description
The blunt-headed salamander is an Ambystomatid or mole salamander from high elevations (2,000m above sea level) 15 miles west of Morelia in Michoacán, Mexico. Mole salamanders are medium to large, stocky salamanders, measuring between 90 to 350mm from the tip of the nose to the end of the tail, which salamanders retain throughout their life. Males are often larger than females, partly due to their longer tails. Ambystomatids generally exhibit both aquatic “neotenic” larval (or aquatic and permanently juvenile in form with external, feathery gills) and terrestrial “metamorphosed” (or ground-dwelling, fully developed adult in form with reduced gills) stages in their wild populations. Ambystomatids are often boldly patterned as adults, with well-developed “costal” grooves (successive vertical grooves along the sides of the body), especially the metamorphosing varieties. They have a rather flattened body with a wide, flattened head, a large mouth and smooth skin with many glands. The tail is roundish or laterally compressed, and, during the breeding season, males display a very swollen cloacal zone (the region around the reproductory and excretory opening in amphibians located underneath the base of the tail).The blunt-headed salamander has both neotenic and fully developed terrestrial (or ground-dwelling) populations. Neotenic populations retain their gills and fins throughout their life, whereas metamorphosed individuals develop adult traits, such as the lack of gills, functioning lungs, eyelids and no fins. These so-called “neotene” individuals are very long with extremely short, blunt heads and round eyes. They are about 150-160 mm in length, with a tail length of around 60-70 mm. The neotenous adults have a dorsal fin along the tail and relatively short, thick gills, although metamorphosed adults lack both fins and gills. The digits are semi-webbed. The colouring of this species is blackish-brown on the dorsal (or upper) surfaces, with a lighter grey under-belly. The end of the tail is darker than the base. The chest and throat have some cream markings. They also display small, dark marks on their head and back.
Ecology
The blunt-headed salamander is a metamorphosing species of mole salamander, which means that it can make the full transition from aquatic larval form to a terrestrial adult form in its lifetime in the wild. The adult blunt-headed salamander spends the majority of its time on land in a mosaic of natural grasslands and pine-oak forests.Once the eggs are laid in water they are left to develop with no further participation by either parent. This species does not exhibit parental care.
Habitat
The blunt-headed salamander inhabits a mosaic landscape of natural grasslands and pine-oak forest, occurring at about 2,000m above sea level in its small range area around Tacicuaro, north-western Michoacan, to the west of the Morelia City in Mexico. Blunt-headed salamanders require ponds of moderate depth in which to breed, and are able to survive in some types of modified landscape, taking advantage of cattle ponds for larval development.
Distribution
Found in the neotropics in a small area around Tacicuaro, north-western Michoacan, to the west of Morelia City in Mexico. It occurs at about 2,000m above sea level.
Population Estimate
There is very little information on the species' population status; there has been limited fieldwork carried out on this species since the early 1980s.
Population Trend
The IUCN Red List of Threatened Species indicates that the blunt-headed salamander’s total population size is generally in decline.
Status
Listed as Critically Endangered on the IUCN Red List of Threatened Species because its extent of occurrence is less than 100km sq. and its area of occupancy is less than 10km sq., its distribution is severely fragmented, and there is continuing decline in the number of mature individuals and in the extent and quality of its habitat around the city of Morelia.
Threats
The desiccation, pollution, and conversion of former ponds, small reservoirs, and open habitat to row crops, represents the main threat to the blunt-headed salamander, coupled with urban expansion of Morelia and Uruapan. Introduced predatory fish are also a major concern, both in ponds and small streams as these may prey extensively on the declining populations of blunt-headed salamanders.
Conservation Underway
The blunt-headed salamander does not occur in any protected areas, although it is protected under the category Pr (Special Protection) by the Government of Mexico.

Chinese Giant Salamander (Andrias davidianus)

The Chinese giant salamander is the largest living species of amphibian, reaching a maximum length of 1.8 metres. It lives in cool, fast-flowing streams and mountain lakes and predominantly feeds on fish and crustaceans. The breeding season occurs between August and September when 500 eggs are laid in a burrow guarded by the male. This species is threatened by over-harvesting for the food trade, as well as the destruction and degradation of its habitat. It is now Critically Endangered, having undergone a massive population decline over the last 30 years.

Evolutionary Distinctiveness
Order: Caudata
Family: Cryptobranchidae
There are only 3 living species of giant salamander in the family Cryptobranchidae. Ancestors of the Cryptobranchidae diverged from all other amphibians over 170 million years ago during the Jurassic Period, which makes this family of amphibians one of the longest unbroken lineages present amongst the modern species assemblages of caecilians, salamanders, frogs and toads. The genus Andrias is represented by only 2 extant species.Cryptobranchids are believed to be derived from hynobiid-like amphibians (relatively primitive small- to medium-sized salamanders found primarily in Asia) due to the retention of larval characters into adulthood (a process called “neoteny”). The fossil record of cryptobranchid salamanders begins with Cryptobranchus saskatchewanensis from the Upper Paleocene to the Lower Eocene (52-58 million years ago), Cryptobranchus scheuchzeri from the Middle Oligocene to the Upper Pliocene in Europe (2-33 million years ago), and Cryptobranchus matthewi from the middle Miocene to the Miocene-Pliocene boundary (14-21 million years ago). The American hellbender Cryptobranchus alleganiensis is also known from the Pleistocene of North America (up to 1.8 million years ago), and the Japanese giant salamander Andrias japonicus is known from the Pleistocene of Asia (1.8 million years ago).

Description
The permanently aquatic Chinese giant salamander is heavily built, with a flat, broad head and a truncated snout. It has a wide mouth, small round eyes that lack eyelids, and small, rounded nostrils close to the edge of the upper lip at the corners of the snout. The species has a large tongue and possesses vomerine teeth (two small bumps found on the roof of the mouth or palate) in addition to a long arc of maxillary (or jaw) teeth.The body, like the head, is quite flattened in appearance, with a broad, compressed tail almost 60% of the body length. The species has a series of costal grooves (found along the sides of the body in the region of the ribs), as well as a vertebral groove (running along the back) and a fold of skin present along the sides of the body from the back of the head to the tip of the tail. The skin is generally rough and porous with numerous wrinkles, folds and tubercles (small bumps). Individuals are dark brown, black or greenish in colour with irregularly blotched, marbled or and/or spotted patterning.Total body length at adulthood is about 1 metre, although a classic publication on the Chinese salamander by M.L.Y. Chang in 1936 quotes a maximum length of 180 cm (1.8 metres). Individuals of 115 cm weigh over 11 kg. This makes the Chinese giant salamander the largest extant amphibian species in the world, both in terms of length and mass, although its close relative the Japanese giant salamander can also reach lengths of 100 m. However, due to wild harvesting of the Chinese giant salamander as a delicacy in Asia, most animals found today are considerably smaller.
Ecology
The breeding season for Chinese giant salamanders appears to occur between August and September. Mating behaviour described for Japanese giant salamanders is probably similar for the Chinese giant salamander. Females lay a string of approximately 500 eggs (each measuring on average 22 mm by 19.2 mm, with an embryo diameter of 8-9 mm) in an underwater burrow or “breeding cavity” that is occupied by a male. The occupying male will aggressively guard this breeding cavity against any intruders. Females may enter the cavity and leave it directly after spawning. Eggs are fertilised externally and then guarded by the male until they hatch after 50-60 days.Chinese giant salamander larvae resemble the adults in shape, and develop in streams. They are only 30 mm in length upon hatching, and start eating after about 30 days. The external gills of the larvae start to reduce in size when they measure 200-250 mm in length, although adults never fully lose two of their gill branches. The larvae have longer gills than those of Japanese giant salamander, their fingers and toes are more pointed, and they are darker in colour. Chinese giant salamanders are very long-lived, reaching ages of more than 52 years in captivity, and are thought to reach sexual maturity at around 15 years.The Chinese giant salamander is generally nocturnal, although they become more diurnal during the breeding season. During the day, the species will usually be found in dark hiding places, venturing out only to stalk their prey and feed. They feed on a wide variety of prey items, such as fish, worms, insect larvae, anurans (frogs and toads) and their tadpoles, crustaceans, molluscs, aquatic reptiles and small mammals. Chinese giant salamanders are also known to eat carrion, their own shed skin and eggs, and may also exhibit cannibalistic behaviour. However, usually the majority of the adult’s diet will simply consist of crustaceans and fish. Chinese giant salamander teeth are small but numerous. The bite is very powerful and provides a strong grip on their prey. The fusion point of the upper and lower jaw of this species is flexible, with large bundles of elastic cartilage that allow the gape of the mouth to reach 40°. The feeding method employed in this species is known as asymmetrical buccal suction, where the lower jaw is depressed quickly and nearby prey items are sucked into the mouth. They have very small eyes positioned far back on the sides of their head that provide them with poor vision – both eyes cannot focus on the same object at the same time. They therefore rely heavily of smell and touch to find their prey.Chinese giant salamanders possess lungs, though which they are able to breathe inefficiently, but they primarily take up oxygen from the water through their skin. As their larval gills become reduced, adults develop a conspicuous fold of skin along their flanks to increase the surface area for oxygen uptake. Their large size, lack of gills and inefficient lungs confine this species to flowing water.

Habitat
The habitat of the Chinese giant salamander consists of rocky, mountain streams and lakes with clear, fast-running water. The species is usually found in forested areas at moderate altitudes, below 1500 m above sea level and especially between 300 and 800 m. Chinese giant salamanders occupy underwater hollows and cavities, and spend their whole lives in water.
Distribution
The Chinese giant salamander is widespread in central, south-western and southern China, although its range is now very fragmented. It occurs from 100–1,500 m above sea level in the mountain stream tributaries of the Pearl, Yellow and Yangtze Rivers. The species ranges from Qinghai and Sichuan to Guangxi, Guangdong and Jiangsu provinces. The population in Taiwan has probably been introduced from mainland China.

Population Estimate
No accurate population estimate is currently available, although it is known that this species was once reasonably common but has declined catastrophically over the last thirty years, principally due to over-exploitation for the food market since at least the 1960s because its meat is considered to be a delicacy in China. It is now very rare, with few known surviving populations.
Population Trend
The Chinese giant salamander is thought to be in decline by the IUCN Red List of Threatened Species. This decline is believed to be severe according to the reports of a number of recent population assessments for this species. Not only have populations become smaller and more fragmented, the individuals captured are smaller than they used to be, most probably as a result of over-collecting of large individuals. Additionally, the generation length is estimated to be 15 years, making population recovery much slower than for many other amphibian species.From catch rates of Chinese giant salamanders it is clear that there has been a very serious decline in their numbers. In the 1960s, more than 15,000 kg of Chinese giant salamander meat was harvested each year from one single Prefecture in Hunan province. In the 1970s, only around 2,500 to 3,000 kg could be harvested each year and this figure has been declining sharply ever since.
Status
The Chinese giant salamander is listed as Critically Endangered in the IUCN Red List of Threatened Species because of an observed drastic population decline, estimated to be more than 80% over the last three generations (since the 1960s), due to over-exploitation.

Threats
Commercial over-exploitation for human consumption is the main threat to the Chinese giant salamander. They are considered to be both a luxury food item and an important source of traditional medicines in China. A factor that renders the Chinese giant salamander particularly vulnerable to hunting is that they are easy to catch – they hide in rock crevasses and may be easily found and hooked out of their hiding place. They remain a lucrative option for hunters, who can sell the flesh for around US$100 per kg (or £30 per lb). Although there is commercial farming and breeding of this species, the vast majority of Chinese giant salamanders being traded are believed to originate from the wild and their harvesting is neither regulated nor managed.This species has also suffered from habitat destruction, for example from the construction of dams which convert their free-flowing stream habitats into standing water or dry them up completely. Habitat degradation is also of grave concern to this species, especially factors such as water pollution from mining activity and farming throughout its range. Other threats to the Chinese giant salamander’s habitat includes deforestation around the streams inhabited by this species. This exacerbates soil erosion and causes increased runoff and siltation of the streams, reducing water quality and making it difficult for this species to get enough oxygen through its skin.
Conservation Underway
The Chinese giant salamander is listed on Appendix I of CITES (the Convention on International Trade in Endangered Species of Wild Fauna and Flora). Appendix I includes species threatened with extinction, and trade in specimens of these species is permitted only in exceptional circumstances. Unfortunately, although CITES regulates international trade in the species, it has no jurisdiction over the domestic trade within China which constitutes the primary market. It is also listed as a Class II State Major Protected Wildlife Species in China.This species occurs, or at least used to occur, in many nature reserves within its range, and some nature reserves even use the Chinese giant salamander as their main conservation target, such as Zhangjiajie Giant Salamander Nature Reserve. There are currently six “Giant Salamander Reserves” in China: Lushi; Qingyaoshan; Youyang; Taibai; Yongshun; and Zhangjiajie. Unfortunately, all of these reserves are adversely affected by a combination of negative factors such as shortage of funding and personnel, lacking a conservation action plan, poaching, uncertain reserve status, and a lack of protection for salamander habitat.In 1999 a huge 99,975 hectare area of Mount Wuyi, China was designated as a World Heritage Site, dedicated to conserving this biodiverse region, including the habitat of the Chinese giant salamander. The surrounding area has a growing population and there are concerns that development around the reserve and increased tourist activity within the reserve will place pressure on Mount Wuyi’s rich natural resources. Captive ranching of animals has achieved some success at reducing the pressure on the dwindling reserves of wild salamanders, but these projects are mainly to meet the market demand. It is likely that these animals are being bred in captivity, although this may involve the use of artificial hormones and breeding it not carried out in conjunction with any re-introduction purposes for conservation purposes.